The Clean Air Act of 1990 imposed stringent restrictions on the amounts and types of materials that can be emitted into the atmosphere. One category of chemicals which was targeted for lower emissions is volatile organic compounds (VOCs). Although not specifically considered hazardous air pollutants, this group of materials is thought to contribute to the overall lowering of air quality.
Many high VOC content materials are excellent solvents and possess excellent cleaning properties. Such materials include low to intermediate flash point mineral spirits, lower alkyl aromatic hydrocarbons, terpene hydrocarbons, low molecular weight alcohol glycol ethers, ether acetates, and ketones. However, because of environmental regulation and related concerns, less hazardous alternatives have been sought.
For example, petroleum or vegetable oils have been mixed with high VOC solvents. However, the resultant products have proven unsuitable, due to the tendency of the petroleum or vegetable oil to impart high viscosity to the final product. High viscosity adversely affects the application and removal of the cleaning product. Furthermore, odor can be a problem, particularly with vegetable oils, because they can become rancid due to oxidation. Finally, these products are unsuitable for the removal of certain types of soil, such as some printing inks.
Prigge, U.S. Pat. No. 4,734,215, attempted to combine a major amount of a saturated hydrocarbon with a minor amount of at least one alkylated aromatic compound. The saturated hydrocarbon was an aliphatic and/or cyclo-aliphatic compound. Saturated hydrocarbons were incorporated because these were considered non-toxic.
Krawack, U.S. Pat. Nos. 5,143,639 and 5,380,453, discloses an emulsion of a C.sub.1 -C.sub.5 alkyl ester of an aliphatic C.sub.8 -C.sub.22 monocarboxylic acid as an ink remover.
Folkard et al., U.S. Pat. No. 5,194,173 removed inks and other oily contaminants from printing machines, printing plates, and offset blankets with a cleaning aid based on a C.sub.6 or higher alkyl ester of a fatty acid, and preferably a C.sub.8 -C.sub.22 fatty acid.
Woo et al., U.S. Pat. No. 5,232,632, disclose a detergent composition utilizing a C.sub.6 -C.sub.9 alkyl aromatic, and particularly an alkyl benzene, as a hydrophobic solvent in combination with a mixture of non-ionic and zwitterionic detergent surfactants. The use of any other solvents is not disclosed.
Principato, U.S. Pat. No. 5,340,493, discloses cleaning compositions which include a tall oil fatty acid ester, organic solvents and optionally, a surfactant.
It has now been discovered that particular alkyl esters of fatty acids, when combined with non-cationic surfactants, and optionally a coupling agent, provide effective low VOC content, general purpose cleaning/degreasing compositions.